EP1258872B1

EP1258872B1 - High-density disk having a protruding portion on a clamping zone

Info

Publication number: EP1258872B1
Application number: EP02005461A
Authority: EP
Inventors: Jin Yong Kim; Kyung Chan Park
Original assignee: LG Electronics Inc
Current assignee: LG Electronics Inc
Priority date: 2001-05-14
Filing date: 2002-03-09
Publication date: 2009-10-14
Anticipated expiration: 2022-03-09
Also published as: EP1605451A1; ES2332036T3; CN1266691C; US20040257941A1; EP1605451B1; DE60231924D1; CN1870154A; ATE428172T1; CN1870154B; CN1385848A; HK1100193A1; CN100372007C; DE60233995D1; EP1258872A2; KR100378086B1; JP2002342978A; US7012880B2; US7515524B2; PT1258872E; EP1258872A3

Abstract

The present invention relates to a high-density disk (20) that is structured to prevent a collision of an optical pickup's objective lens with the high-density disk if the disk is placed upside down in a disk device that is able to record and reproduce signals to/from the high-density disk. A high-density disk recording medium according to the present invention is structured such that, wherein a recording layer having high-density pit patterns is offset from a center plane of disk thickness, both sides of a clamping zone bisected by the center plane have differing thicknesses (P1,P2). One or both sides may protrude from surface of the disk recording medium, or one side of the clamping zone may protrude from the surface while the other side is indented below the surface.

Description

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a high-density disk structure preventing collision of ain optical pickup's objective lens with a high-density disk which is placed upside down in a disk device being able to reproduce and record signals from/to a high-density disk such as a high-density digital versatile disk (called "HD-DVD" hereinafter).

Description of the Related Art

JP 10269620 (abstract) relates to an optical disk having a substrate which passes light beams for reading and writing. With respect to a center plane of the disk, a recording layer is located in a portion of the disk which is distant from a light beam entrance side.
A central portion of the substrate has a protrusion on the light beam entrance side.
A compact disk, usually called "CD," is 1.2mm in thickness and 120mm in diameter as shown in Fig. 1. A CD has a center hole of 15mm diameter and a clamping zone of 44mm, which encircles the center hole where the clamping zone is clamped by a clamper on a spindle or a turntable installed in a disk device.
When a CD is normally placed into a disk device, its recording layer, which has pit patterns, is approximately 1.2mm from an objective lens of an optical pickup equipped in the disk device. The objective lens for a CD has a numerical aperture (NA) of 0.45, which is relatively small.
A digital versatile disk, usually called "DVD," is 1.2mm in thickness and 120mm in diameter like a CD as shown in Fig 2. A DVD also has a center hole of 15mm diameter and a clamping zone of 44mm encircling the center hole.
When a DVD is normally placed into a disk device, its recording layer, which has pit patterns, is approximately 0.6mm from an objective lens of an optical pickup equipped in the disk device. The objective lens for a DVD has a NA of 0.6, which is relatively large.
A HD-DVD, which is currently being commercialized, is 1.2mm in thickness and 120mm in diameter, like a CD as shown in Fig. 3. A HD-DVD also has a center hole of 15mm diameter and a clamping zone of 44mm encircling the center hole. If a HD-DVD is normally placed into a disk device, there will be a 0.1 mm gap between its recording layer, which also has pit patterns, and an objective lens of an optical pickup for a HD-DVD, which has the largest NA of 0.85. The optical pickup for a HD-DVD uses a laser beam of shorter wavelength than for a CD or a DVD to record or reproduce signals in high density.
Therefore, in comparison with a CD or a DVD, HD-DVD uses an objective lens that is situated closer to the recording layer, that uses a laser beam of shorter wavelength, and that has a greater NA. According to these conditions, it is possible to concentrate a stronger intensity of light on a smaller beam spot formed on the high-density pit patterns of the recording layer of the HD-DVD. Consequently, the transmitting distance of a laser beam of shorter wavelength is shortened, and the variation of the laser beam and its spherical aberration are minimized.
If a HD-DVD 10 is normally placed onto a turntable 11 installed in a disk device as shown in Fig. 4, a conventional servo-controlling operation for a spindle motor 12 by a motor driving unit 13 and a servo controller 15 is conducted to rotate the placed HD-DVD 10 at a constant and high speed. While the HD-DVD 10 is rotating, a focusing-servo operation is conducted to focus a laser beam for an optical pickup 14 exactly onto the recording layer 9. This operation is performed by moving the objective lens OL of the optical pickup 14 in an up and down direction within an operating distance OD. If a laser beam is exactly in focus, then reproduction (or recording) of high-density pit patterns can be accomplished.
However, when the HD-DVD 10 is misplaced onto the turntable 11 by, for example, being placed upside down as shown in Fig. 5, the HD-DVD 10 will still be rotated at a constant and high speed by the combined servo-controlling operation by the spindle motor 12, the motor driving unit 13, and the servo controller 15. However, if the HD-DVD 10 has been placed upside down, the gap between the recording layer 9 and the objective lens OL of the optical pickup 14 is 1.1mm greater in comparison with a normally-placed HD-DVD.
In this misplacement, a laser beam cannot be focused within the conventional operating distance of the objective lens OL of the pickup 14. Therefore, the servo controller 15 supervising the focusing-servo operation continues to move the objective lens OL upward to the maximum movable distance 'OD_Max' until the laser beam is correctly focused. However, in this case, the objective lens OL will collide with the misplaced HD-DVD 10. Consequently, the HD-DVD 10, the objective lens OL, and/or the servo-mechanism would be irreparably damaged.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a high-density disk structured to prevent the collision of an objective lens of an optical pickup and the high-density disk even though the objective lens moves upward to maximum movable distance, and to enable the detection of the misplacement of a high-density disk as no disk state through a conventional focusing operation on the condition that the high-density disk has been placed upside down.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings. The invention is defined by the appended claims.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide a further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a further understanding of the invention, illustrate the preferred embodiments of the invention, and together with the description, serve to explain the principles of the present invention.

Fig. 1 shows the structure of a conventional compact disk (CD);
Fig. 2 shows the structure of a conventional digital versatile disk (DVD);
Fig. 3 shows the structure of a conventional high-density DVD (HD-DVD);
Figs. 4 and 5 show normal placement and misplacement of a conventional high-density DVD, respectively;
Fig. 6 is a sectional view of the first embodiment of, for example, a high-density disk structured according to the present invention;
Figs. 7 and 8 show normal placement and misplacement, respectively, of the first embodiment of a high-density disk structured according to the present invention;
Fig. 9 is a sectional view of the second embodiment of a high-density disk structured according to the present invention;
Figs. 10 and 11 show normal placement and misplacement, respectively, of the second embodiment of a high-density disk structured according to the present invention;
Fig. 12 is a sectional view of the third embodiment of a high-density disk structured according to the present invention; and
Figs. 13 and 14 show normal placement and misplacement, respectively, of the third embodiment of a high-density disk structured according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In order that the invention may be fully understood, a preferred embodiment thereof will now be described with reference to the accompanying drawings.
Fig. 6 is a sectional view of the first preferred embodiment of a high-density disk structured according to the present invention. The embodiment of a high-density disk, for example, a HD-DVD according to the present invention has same dimension as a conventional HD-DVD depicted in Fig. 3, namely, 1.2mm in thickness and 120mm in diameter, a center hole of 15mm diameter and a clamping zone (or clamping area) of 44mm diameter encircling the center hole. In addition, when the present HD-DVD 20 of Fig. 6 is normally placed into a disk device, its recording layer, which contains pit patterns, would be approximately 0.1mm from the objective lens of an optical pickup as mentioned before.
However, the present HD-DVD 20 in Fig. 6 has a clamping zone structured such that the thickness (P1 and P2) of each side, P1 and P2, are different, namely and preferably P1 is greater than P2. P1 and P2 are created by bisecting the clamping zone with an imaginary longitudinal center plane "c." In order for both sides to have different thicknesses, the opposite side of the recording side, which is the recording layer, protrudes above the disk's upper surface, indicated by D1 in Fig. 6. Because it is not necessary for the entire clamping zone to have a different thickness, the clamping zone may have partial regions that are protruding or raised with respect to the recording or reading area of the disk.
The height D1 preferably ranges from about 0.1mm to 0.6mm and guarantees a marginal gap between the present disk and the objective lens for preventing a collision between the objective lens of an optical pickup even though the objective lens moves upward to the maximum movable distance on the condition that the present high-density disk has been placed upside down. Alternatively, other suitable height D1 may also be used without deviating from the present invention.
If the disk 20 structured as above is placed normally on a spindle or turntable 11 equipped in a disk device as shown in Fig. 7, the non-protruding side of the clamping zone of the present disk 20 is in contact with the turntable 11. Consequently, the disk 20 is normally clamped the same as a conventional disk.
After successful clamping of the high-density disk 20, a conventional servo-controlling operation, characterized by the operation of the spindle motor 12, the motor driving unit 13 and the servo controller 15, is conducted to rotate the right-clamped disk 20 at a constant and high speed. Subsequently, a focusing-servo operation is conducted to focus a laser beam exactly onto a recording layer by moving the objective lens OL of the optical pickup 14 up and down within the operating distance OD. Once the laser beam is exactly focused, reproduction (or recording) of the high-density pit patterns begins.
However, if the present disk 20 is placed upside down on the turntable 11 as shown in Fig. 8, the protruding side of the clamping zone of the present disk 20 is in contact with the turntable 11. Consequently, the surface of the disk 20 is raised by the height D1 over normal placement, which ranges from about 0.1mm to 0.6mm. In other words, the separation distance between the objective lens and the disk 20 has increased due to the added thickness of the clamping zone.
Therefore, although the objective lens OL of the optical pickup 14 moves up to the maximum distance to acquire the exact focus while the misplaced disk 20 is rotating at a high speed, the objective lens OL will not collide with the surface of the misplaced disk 20, due to the marginal gap D1 created by the protruding side of the clamping zone. Furthermore, because the recording layer, and the high-density pit patterns contained within, is also further apart from the objective lens OL than in normal placement, the focusing operation will fail. As a result, the misplacement of the disk would be judged as "no disk." Because a judgment of "no disk" ceases the focusing operation, a collision between the objective lens OL and the disk 20 is avoided.
Fig. 9 is a sectional view of the second preferred embodiment of a high-density disk structured according to the present invention. The second embodiment of a high-density disk 21 according to the present invention has a clamping zone structured such that the thickness of each side, P1 and P2, which are created by bisecting the clamping zone with an imaginary longitudinal center plane "c," are different. Namely, P1 is greater than P2, where both P1 and P2 are both greater than one-half of the whole thickness of the disk 21 as shown in Fig. 9. The side opposite to the recording side protrudes from disk surface a greater distance than of the recording side. As shown in Fig. 9, the height D1, which ranges approximately from 0.1mm to 0.6mm, is greater than D2, which is located on the recording side.
The protruding height D2 of the recording side is preferably determined to be within a range that ensures a successful focus of the pit patterns within the recording layer by the objective lens OL as it moves up and down within the operating distance OD on the condition that the disk 21 has been normally placed.
Therefore, if the high-density disk 21 structured as above is placed normally on the turntable 11, the recording layer of the disk 21 is further apart from the objective lens OL by the small protruding height D2 than that of a conventional disk. However, because the distance D2 is within a range ensuring successful focus as described above, it is possible to focus a light beam on the recording layer so that reproduction (or recording) of the high-density pit patterns can be conducted.
If the high-density disk 21 is placed upside down on the turntable 11 as shown in Fig. 11, the surface containing the protruding side of the clamping zone that measures in height D1 is situated higher by the same height D1, similar to the situation depicted in Fig. 8. Consequently, the objective lens OL of the optical pickup 14 can move up to the maximum distance to acquire an exact focus while the misplaced disk 21 is rotating at a high speed without colliding with the surface of the misplaced disk 21. Also, because the recording layer is further apart from the objective lens OL by the height D1, the focusing operation will fail, resulting in that the disk misplacement would be judged as "no disk." Because judgment of 'no disk' ceases all focusing operations, a collision between the objective lens OL and the disk 21 is avoided.
Fig. 12 is a sectional view of the third preferred embodiment of a high-density disk structured according to the present invention. The third embodiment of a high-density disk 22 according to the present invention has a clamping zone structured such that the thickness of each side, P1 and P2, which are created by bisecting the high-density disk 22 with an imaginary longitudinal center plane "c." In this case, P1 is greater than P2 and P1 is thicker than one-half of the whole thickness of the disk 22 but P2 is thinner than one-half of the whole thickness of the disk 22. The side opposite to the recording side protrudes from disk surface by the height D1, which ranges from approximately 0.1mm to 0.6mm, whereas the clamping zone on the recording side is indented by a height less than D1.
Therefore, if the high-density disk 22 structured as above is placed normally on the turntable 11, the indented side of the clamping zone, which is in contact with a holder of the turntable 11, allows the recording layer of the disk 22 to be appropriately apart from the optical pickup 14. However, the distance between the recording layer and the objective lens OL for this embodiment is longer within the acceptable range for a conventional disk.
In this situation, an exact focus on the recording layer is acquired through moving the objective lens OL up and down within the operating distance OD, which can then result in the reproduction (or recording) of high-density pit patterns.
If the present disk 22 is placed upside down on the turntable 11 as shown in Fig. 14, the surface of the disk 22 is raised by a height D1, which ranges from 0.1mm to 0.6mm. Therefore, although the objective lens OL of the optical pickup 14 can move up to the maximum distance to acquire an exact focus on the recording layer, the objective lens OL will not collide with the surface of the misplaced disk 22. As described above, the misplacement would result in a reading of "no disk," which would cease the focusing operation and avoiding a collision between the objective lens OL and the disk 22.
In addition, the protrusion and/or indentation of the claming zone may be shaped variously other than the aforementioned embodiments, for example, a clamping zone may be protruded or indented partially.
The invention may be applicable to a rewritable high-density disk as well as a read-only high-density disk without departing from the sprit or essential characteristics thereof. Alternatively, the present invention may also be applied to any other rewritable or read-only type disk medium. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description.

Claims

An optical disk (20, 21, 22) for storing data having
first and second surfaces, the second surface being an entrance surface with respect to a recording or reproducing light beam and being parallel to the first surface;

a clamping area including first and second clamping surfaces;

a first side having the first surface and the first clamping surface;

a second side having the second surface and the second clamping surface;

a center plane (c) being located in the middle between the first surface and the second surface;

a center hole having a predetermined diameter; and

a recording layer being located between the center plane (c) and the second surface, characterized in that

the clamping area has a protruding portion on the first clamping surface,
wherein the clamping area at the protruding portion has first and second thickness (P1, P2) measured from the center plane of the disk (20, 21, 22), the first thickness (P1) measured in a direction extending from the center plane (c) of the disk (20, 21, 22) toward the first clamping surface of the clamping area and the second thickness (P2) measured in a direction toward the second clamping surface, wherein the first thickness (P1) is greater than the second thickness (P2) and wherein the recording layer is located at about 0.1mm from the second surface.
The optical disk (20, 21, 22) of claim 1, wherein a difference between the first and the second thicknesses (P1, P2) is approximately 0.1mm to 0.6mm.
The optical disk (20) of one of the preceding claims, wherein:
the second clamping surface is located concentrically within the second side and is level with the second surface of the second side; and

the first clamping surface is located concentrically within the first side and protrudes from the first surface of the first sides.
The optical disk (21) of one of claims 1 to 2, wherein:
the first clamping surface is located concentrically within the first side and protrudes from the first surface of the first side; and

the second clamping surface is located concentrically within the second side and protrudes from the second surface of the second side.
The optical disk (21) of claim 4, wherein the first side clamping zone protrudes from the first surface of the first side a distance (D1) greater than the distance (D2) the second side clamping zone protrudes from the second surface of the second side.
The optical disc (22) of one of claims 1 to 2, comprising:
the second clamping surface is located concentrically within the second sided and is indented from the second surface of the second side; and

the first clamping surface is located concentrically within the first side and protrudes from the first surface of the first side.
The optical disk (21, 22) of one of claims 4 to 6, wherein the first side clamping zone protrudes from the first surface of the first side a distance (D1) of about 0.1mm to 0.6mm.
The optical disk (22) of one of claims 6 or 7, wherein the second side clamping zone is indented from the second surface of the second side a distance (D1) of about 0.1mm to 0.6mm.
Recording medium comprising an optical disk (20, 21, 22) according to one of the preceding claims.